Abstract : As predicted by thermodynamic studies of polymer conformation, high molecular weight poly(methyl methacrylate), PMMA, dissolves cleanly, and at a constant rate, in a 7:3 mixture of 1-butanol and acetonitrile although neither liquid is a solvent for PMMA by itself. Mixtures of other alcohols with acetonitrile also dissolve PMMA. When mixture with the same fraction of acetonitrile are compared, methanol dissolves PMMA almost twice as fast, ethanol and hexanol at about the same rate, and 2-propanol somewhat more slowly than the 1-butanol mixture with acetonitrile. The measurements of dissolution rate were made using a laser interferometer at 20 C. Keywords: Microlithography, Resists, Poly(methyl methacrylate). (aw)